Can a Taillight Converter Module Go Bad After Working Properly for Months

Updated 04/24/2019 | Published 04/22/2019

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T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector

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$73.40

Hook Probe Circuit Tester

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$13.21

Question:

Can a Taillight Converter Module Go Bad After Working Properly for Months Your original reply makes the comment to suspect the converter if upstream tow vehicle lamps work fine but there is no output from the converter. In my case, the tow vehicle lamps are work fine, but the converter puts out full voltage to running lamp and one turn lamp without any vehicle lamps on. The other turn lamp will blink with vehicle turn lamp. This is checked against a trailer that works fine with alternate tow vehicle. I would like you to update your troubleshooting guide for confirming converter is bad with some, but bogus, voltage out. Something with a recipe of connect wires this way and check these terminals, that I could prove/disprove the converter function. In my case, I could unplug the converter for bench testing and get the same result: power and ground into convert delivers same parking/one turn steady power out. I also uncovered the loom to confirm no melts/shorts/bad insulation on the wires. BTW my controller is Curt high capacityinch S0612U-R1

asked by: Hugh P

Expert Reply:

Unfortunately a trailer wiring converter module like # 118426 can go bad at any time without any notice. It is rare, but can happen. The module has a circuit board that will work great until it doesn't and if that goes, it can do some odd things like what you are experiencing.

If you test the wires going into the control module and there is no issue, then you have function issues after the converter, it is safe to determine the converter module is bad and needs replaced. If your vehicle lights are working fine when the module is disconnected and then have issues when connected this is also a sign of a bad converter that is back feeding. The only thing I recommend prior to dismissing the converter is to make sure you have a good ground connection and you are getting the correct power and that you connections to your factory harness is clean with no bent pins or corrosion. Bent pins or corrosion can be an issue that causes power to jump from one function to another that can disrupt the converter.

I recommend using a circuit tester like # PTW2993 to test each function at your tail lights then right after the connection. Then test again right before the converter and then directly after the converter. If you can isolate the issue to the box, then you have confirmed the bad converter. If however you get the correct functions at the back trailer side of the converter and it doesn't transfer to the pins correctly then you have a wire short issue.

If everything checks out on the vehicle side, yet a trailer that works with other vehicles still doesn't work, there can be a wiring issue on the trailer that will still allow function with some and not with others. Let me know if we need to continue troubleshooting on that end.

expert reply by: Jason S